The presence of amyloid β-protein in the detergent-insoluble membrane compartment of human neuroblastoma cells

To investigate the intracellular compartmentalization of amyloid beta-protein (A beta), human neuroblastoma SH-SY5Y cells were fractionated and the A beta content in each fraction was quantitated by the well-characterized two-site enzyme-linked immunosorbent assay (ELISA). Subcellular fractionation of the cell revealed two distinct pools of A beta within the cells: a Triton-soluble and a Triton-insoluble pools with the latter being larger than the former. Because Triton insolubility points to caveolae-like domains, we prepared detergent-insoluble, low-density membrane domains from SH-SY5Y cells using two different protocols. The low-density membrane fraction prepared by either protocol was found to contain a substantial proportion of intracellular A beta 40 and A beta 42. These results indicate that the distinct membrane domains are involved in the generation and/or trafficking of A beta.